V. Guerrero de la Rosa et al. / Tetrahedron: Asymmetry 12 (2001) 1615–1620
1619
mg, 63%) as a white solid; mp 86–88°C; [h]D=+10.3 (c
Column chromatography (ethyl acetate:methanol 4:1)
1
of the reaction crude afforded N-(benzyloxycarbonyl)-
2.7, acetone); H NMR (500 MHz, CDCl3): l 7.30 (s,
(R)-S-methyl-S-oxo- -cysteinol (RC,RS)-8 as a white
L
5H, C6H5), 6.26 (br, 1H, NH), 5.07 (s, 2H, CH2O), 4.66
(m, 1H, CH), 3.73 (s, 3H, CH3O), 3.24 (m, 2H, CH2S),
2.57 (s, 3H, CH3); 13C NMR (125 MHz, CDCl3): l
170.1, 155.7, 135.9, 128.4, 128.2, 128.0, 67.1, 55.8, 53.0,
49.9, 38.8. HRMS calcd m/z for C13H17NO5S:
299.0827. Found: 299.0873. Anal. calcd for
C13H17NO5S: C, 52.17; H, 5.72; N, 4.68. Found: C,
51.91; H, 5.74; N, 4.45%.
solid (174 mg, 82%), mp 129–130°C; [h]D=+66 (c 2.12,
1
CHCl3); H NMR (500 MHz, CDCl3): l 7.32 (s, 5H,
C6H5), 5.79 (br, 1H, NH), 5.07 (s, 2H, CH2O), 4.12 (m,
1H, CH), 3.81 (m, 2H, CH2OH), 3.28 (br, 1H, OH),
3.00 (m, 2H, CH2S), 2.60 (s, 3H, CH3); 13C NMR (125
MHz, CDCl3): l 156.0, 136.1, 128.5, 128.2, 128.1 67.0,
63.6, 55.4, 50.0, 39.0. HRMS calcd m/z for
C12H17NO4S: 271.0878. Found: 271.0834. Anal. calcd
for C12H17NO4S: C, 53.12; H, 6.31; N, 5.16. Found: C,
52.94; H, 6.29; N, 4.93%.
3.3.3. (RC,RS)-N-(Benzyloxycarbonyl)-S-oxo-S-propyl-
L
-cysteine methyl ester (RC,RS)-7b. The reaction of sul-
phinate (RC,SS)-6 (0.5 g, 0.92 mmol) with a solution of
n-propyl magnesium chloride (2.76 mmol) following the
general procedure gave, after purification by column
chromatography (AcOEt–methanol 20:1), N-(benzyl-
3.5. (RC,SS)-N-(Benzyloxycarbonyl)-O-methoxymethyl-
S-methyl-S-oxo- -cysteinol (RC,SS)-9
L
To a solution of N-(benzyloxycarbonyl)-S-methyl-S-
oxo- -cysteinol (RC,SS)-8 (80 mg, 0.295 mmol) in dry
oxycarbonyl)-(R)-S-oxo-S-propyl-
L
-cysteine
methyl
L
ester (RC,RS)-7b as a white solid (187 mg, 62%); mp
96–97°C; [h]D=−27 (c 1.5, CHCl3); 1H NMR (500
MHz, CDCl3): l 7.34 (s, 5H, C6H5), 6.20 (br, 1H, NH),
5.12 (s, 2H, CH2O), 4.79 (m, 1H, CH), 3.78 (s, 3H,
CH3O), 3.20 (m, 2H, CH2), 2.73 (m, 2H, SOCH2), 1.82
(m, 2H, CH2), 1.07 (t, J=7.3 Hz, 3H, CH3); 13C NMR
(125 MHz, CDCl3): l 170.5, 155.9, 136.0, 128.3, 128.0,
127.9 67.2, 54.7, 53.8. 52.5, 50.4, 16.1, 13.2. HRMS
calcd m/z for C15H21NO5S: 327.1151. Found: 327.1140.
Anal. calcd for C15H21NO5S: C, 55.03; H, 6.47; N, 4.28.
Found: C, 54.98; H, 6.67; N, 4.18%.
THF (20 mL) cooled at 0°C, was added dropwise a
solution of n-BuLi in hexanes (1.4 M, 630 mL, 0.88
mmol) and methoxymethyl chloride (340 mL, 0.44
mmol) and the reaction mixture was allowed to warm
to rt. After 3 days the reaction was quenched with a
saturated aqueous solution of NH4Cl (15 mL),
extracted with dichloromethane (4×25 mL), dried over
Na2SO4 and concentrated under vacuum. The residue
was purified by flash chromatography (AcOEt–MeOH
95%) to afford N-(benzyolycarbonyl)-O-methoxy-
methyl-(S)-S-methyl-S-oxo- -cysteinol (RC,SS)-9. (80
L
mg, 86% yield) as a white solid, mp 112–113°C; [h]D=
3.3.4. (RC,SS)-N-(Benzyloxycarbonyl)-S-oxo-S-propyl-
1
−76.4 (c 1.1, acetone); H NMR (500 MHz, CDCl3): l
L
-cysteine methyl ester (RC,SS)-7b. The general proce-
7.35 (s, 5H, C6H5), 5.77 (br, 1H, NH), 5.11 (s, 2H,
CH2O), 4.64 (s, 2H, OCH2O), 4.34 (m, 1H, CH), 3.77
(m, 2H, CH2O), 3.35 (s, 3H, CH3O), 3.04 (d, J=6.1 Hz,
2H, CH2S), 2.64 (s, 3H, CH3); 13C NMR (125 MHz,
CDCl3): l 155.7, 136.2, 128.5, 128.5 128.1, 96.8, 68.4,
66.9, 56.1, 55.6 47.9, 39.4. HRMS calcd m/z for
C14H21NO5S: 315.1664. Found: 315.1654. Anal. calcd
for C14H21NO5S: C, 53.31; H, 6.71; N, 4.44. Found: C,
53.36; H, 6.73; N, 4.41%.
dure was followed for the alkylation of sulphinate
(RC,RS)-6 (0.5 g, 0.92 mmol) with a solution of propyl
magnesium chloride (2.76 mmol). Purification of the
reaction mixture by flash chromatography (AcOEt–
methanol 20:1), gave N-(benzyloxycarbonyl)-(R)-S-
oxo-S-propyl- -cysteine methyl ester (RC,SS)-7b (202
L
mg, 67%) as a white solid; mp 124–125°C; [h]D=+36 (c
1
1.0, CHCl3); H NMR (500 MHz, CDCl3): l 7.32 (s,
5H, C6H5), 6.03 (br, 1H, NH), 5.10 (s, 2H, CH2O), 4.69
(m, 1H, CH), 3.76 (s, 3H, CH3O), 3.20 (m, 2H, CH2),
2.27 (m, 2H, SOCH2), 1.72 (m, 2H, CH2), 1.11 (t,
J=7.3 Hz, 3H, CH3); 13C NMR (125 MHz, CDCl3): l
170.2, 155.7, 135.9, 128.5, 128.2, 128.0, 67.2, 54.7, 53.8,
53.1, 50.1, 16.2, 13.5. HRMS calcd m/z for
C15H21NO5S: 327.1151. Found: 327.1129. Anal. calcd
for C15H21NO5S: C, 55.25; H, 6.61; N, 4.06. Found: C,
54.98; H, 6.67; N, 4.18%.
Acknowledgements
The authors would like to thank the Spanish DIGICYT
(Project PB94-1431), the Junta de Andaluc´ıa and the
CONACYT (Project 28762-E) for financial support.
V.G.R. would also like to thank Fundacion Avenzoar
for a scholarship.
3.4. (RC,SS)-N-(Benzyloxycarbonyl)-(S)-S-methyl-S-
oxo- -cysteinol (RC,SS)-8
L
References
To a solution of N-(benzyloxycarbonyl)-(S)-S-methyl-
S-oxo- -cysteine methyl ester (RC,SS)-7a (233 mg, 0.78
L
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mmol) in dimethoxyethane (15 mL) cooled at 0°C was
added dropwise a solution of LiBH4 in THF (2 M, 2.32
mL, 1.16 mmol) and the resulting mixture was stirred
for 1 at rt. Aqueous H2SO4 (3 N, 5 mL) was added and
the reaction mixture was stirred for 10 min. and
extracted with ether (4×50 mL). The organic extracts
were washed with a saturated aqueous solution of NaCl
(25 mL) and concentrated under reduced pressure.
4. Kyong, K. S.; Han, D. C.; Fielding, H. P. J. Food Sci.
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